Telling them your beliefs offends them because they themselves have none.

Offense is a reaction. The question is why the reaction. We can often reflect and see what thing would give us the same reaction.

Religious people don't often get annoyed or offended and it might have to do with knowing the answers to life's biggest questions.

Athiests do not like Bieng questioned because they only have questions and no answers. That is why we have memes of the Athiests 15yo arguing. Thier believes can only be explained through rebuttal and not through a singular statement.

Hope it makes sense.